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Topic Review
Macroplastic
The term macroplastics describes plastic items with a diameter ≥ 5 mm. With this size definition macroplastics can be directly distinguished from microplastics (diameter < 5 mm). Plastic items ≥ 5 mm are commonly considered to be macroplastics once they are released into the environment. Other terminologies used synonymous to macroplastic are “macro litter", “anthropogenic litter”, “plastic litter”, “marine litter”, “marine plastic” and “plastic debris”. 
  • 11.4K
  • 09 Oct 2020
Topic Review
Water Quality Degradation
Water quality degradation is happened through the natural processes that influence the surface water and groundwater quality by various sources such as climate changes, natural disasters, geological factors, soil-matrix, and hyporheic exchange. Water could also be contaminated by anthropogenic factors. Anthropogenic pollutants are substances caused by human actions, mostly resulting from land-use practices. 
  • 11.3K
  • 05 Feb 2022
Topic Review
Human Eye Color
Eye color is a polygenic phenotypic character and is determined by the amount and type of pigments in the eye's iris. Humans and other animals have many phenotypic variations in eye color, as blue, brown, gray, green and others. These variations constitute phenotypic traits. The genetics of eye color are complicated, and color is determined by multiple genes. Some of the eye-color genes include EYCL1 (a green/blue eye-color gene located on chromosome 19), EYCL2 (a brown eye-color gene) and EYCL3 (a brown/blue eye-color gene located on chromosome 15). The once-held view that blue eye color is a simple recessive trait has been shown to be wrong. The genetics of eye color are so complex that almost any parent-child combination of eye colors can occur. In human eyes, these variations in color are attributed to varying ratios of eumelanin produced by melanocytes in the iris. The brightly colored eyes of many bird species are largely determined by other pigments, such as pteridines, purines, and carotenoids. Three main elements within the iris contribute to its color: the melanin content of the iris pigment epithelium, the melanin content within the iris stroma, and the cellular density of the iris stroma. In eyes of all colors, the iris pigment epithelium contains the black pigment, eumelanin. Color variations among different irides are typically attributed to the melanin content within the iris stroma. The density of cells within the stroma affects how much light is absorbed by the underlying pigment epithelium. OCA2 gene polymorphism, close to proximal 5′ regulatory region, explains most human eye-color variation.
  • 11.3K
  • 05 Dec 2022
Topic Review
The Tryptophan-Kynurenine Metabolic Pathway
Tryptophan (TRP) is one of the essential amino acids, which participates in protein synthesis. The tryptophan’s main metabolic route is the kynurenine pathway (KP) through which approximately 90-95% of TRP degrades into nicotinamide adenine dinucleotide (NAD+) and other bioactive metabolites. The appropriate amount of NAD+ is essential to maintain the operation and the viability of cells. The other molecules are neurotoxic, neuroprotective, oxidant, antioxidant, and/or immune modifiers. They play an important role in the function of the brain and the peripheral tissues. The change in the levels of the bioactive molecules is considered to contribute to the development of a wide range of illnesses from cancer to immunologic, neurodegenerative, and psychiatric diseases.
  • 11.1K
  • 10 Aug 2021
Topic Review
Overhead Camshaft
Overhead camshaft, commonly abbreviated to OHC, is a valvetrain configuration which places the camshaft of an internal combustion engine of the reciprocating type within the cylinder heads ("above" the pistons and combustion chambers) and drives the valves or lifters in a more direct manner compared with overhead valves (OHV) and pushrods.
  • 11.1K
  • 21 Nov 2022
Topic Review
Flavonoids—Classification and Natural Sources
       Flavonoids are small molecules, produced de novo by plants as secondary metabolites in response to diverse biotic and abiotic factors. These chemical compounds have a broad spectrum of established health-promoting effects. They are due to their antioxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic properties coupled with their capacity to modulate key cellular enzyme functions. Flavonoids are widely distributed chemical compounds in the plant kingdom. Plants are therefore an inexhaustible source of flavonoids.
  • 11.0K
  • 02 Nov 2020
Topic Review
Relative Hour (Jewish Law)
Relative hour (Hebrew singular: shaʿah zǝmanit / שעה זמנית; plural: shaʿot - zǝmaniyot / שעות זמניות), sometimes called halachic hour, seasonal hour and variable hour, is a term used in rabbinic Jewish law that assigns 12 hours to each day and 12 hours to each night, all throughout the year. A relative hour has no fixed radical, but changes with the length of each day - depending on summer (when the days are long and the nights are short), and on winter (when the days are short and the nights are long). Even so, in all seasons a day is always divided into 12 hours, and a night is always divided into 12 hours, which inevitably makes for a longer hour or a shorter hour. All of the hours mentioned by the Sages in either the Mishnah or Talmud, or in other rabbinic writings, refer strictly to relative hours. Another feature of this ancient practice is that, unlike the standard modern 12-hour clock that assigns 12 o'clock pm for noon time, in the ancient Jewish tradition noon time was always the sixth hour of the day, whereas the first hour began with the break of dawn, by most exponents of Jewish law, and with sunrise by the Vilna Gaon and Rabbi Hai Gaon. 12:o'clock am (midnight) was also the sixth hour of the night, whereas the first hour of the night began when the first three stars appeared in the night sky.
  • 11.0K
  • 19 Oct 2022
Topic Review
Constructivist Epistemology
Constructivist epistemology is a branch in philosophy of science maintaining that scientific knowledge is constructed by the scientific community, who seek to measure and construct models of the natural world. Natural science therefore consists of mental constructs that aim to explain sensory experience and measurements. According to constructivists, the world is independent of human minds, but knowledge of the world is always a human and social construction. Constructivism opposes the philosophy of objectivism, embracing the belief that a human can come to know the truth about the natural world not mediated by scientific approximations with different degrees of validity and accuracy. According to constructivists there is no single valid methodology in science, but rather a diversity of useful methods.
  • 11.0K
  • 28 Nov 2022
Topic Review
Fifth Generation Computer
The Fifth Generation Computer Systems (FGCS) was an initiative by Japan's Ministry of International Trade and Industry (MITI), begun in 1982, to create computers using massively parallel computing and logic programming. It was to be the result of a government/industry research project in Japan during the 1980s. It aimed to create an "epoch-making computer" with supercomputer-like performance and to provide a platform for future developments in artificial intelligence. There was also an unrelated Russian project also named as a fifth-generation computer (see Kronos (computer)). Ehud Shapiro, in his "Trip Report" paper (which focused the FGCS project on concurrent logic programming as the software foundation for the project), captured the rationale and motivations driving this project: The term "fifth generation" was intended to convey the system as being advanced. In the history of computing hardware, computers using vacuum tubes were called the first generation; transistors and diodes, the second; integrated circuits, the third; and those using microprocessors, the fourth. Whereas previous computer generations had focused on increasing the number of logic elements in a single CPU, the fifth generation, it was widely believed at the time, would instead turn to massive numbers of CPUs for added performance. The project was to create the computer over a ten-year period, after which it was considered ended and investment in a new "sixth generation" project would begin. Opinions about its outcome are divided: either it was a failure, or it was ahead of its time.
  • 10.9K
  • 21 Oct 2022
Topic Review
Jet Engine Thrust
The familiar explanation for jet thrust is a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and exit, as explained in "Thrust calculation". As an example, an early turbojet, the Bristol Olympus Mk. 101, had a momentum thrust of 9300 lb. and a pressure thrust of 1800 lb. giving a total of 11,100 lb. Looking inside the "black box" shows that the thrust results from all the unbalanced momentum and pressure forces created within the engine itself. These forces, some forwards and some rearwards, are across all the internal parts, both stationary and rotating, such as ducts, compressors, etc., which are in the primary gas flow which flows through the engine from front to rear. The algebraic sum of all these forces is delivered to the airframe for propulsion. "Flight" gives examples of these internal forces for two early jet engines, the Rolls-Royce Avon Ra.14 and the de Havilland Goblin
  • 10.9K
  • 23 Nov 2022
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